Kao is an island and stratovolcano in Tonga. It reaches 1,030 m above sea level, the highest point in Tonga. The date of its last eruption is unknown, and fresh lava flows are not seen, but the absence of deep erosional gullies or high sea cliffs suggests a very recent origin. It lies about 6 km north of Tofua island. The slopes of the island rise at angles exceeding 35 degrees to the summit, which has a series of small volcanic craters. The island is densely jungled on its lower flanks, while the upper slopes are almost bare.